Multiple redundant power supply

ABSTRACT

A multiple redundant power supply for supplying a substantially constant voltage to output terminals is disclosed in accordance with the teachings of the present invention. A first pair of voltage sources is coupled to one output terminal and a second pair of voltage sources is coupled to another output terminal and connected in series with the first pair of voltage sources. Steering diodes are provided such that a series connection obtains between either one of the voltage sources included in the first pair and either one of the voltage sources included in the second pair. First switch means interconnects the voltage sources included in the first pair and is adapted when activated to provide a series connection between the first pair voltage sources. Second switch means interconnects the voltage sources included in the second pair and is adapted when activated to provide a series connection between the second pair of voltage sources. The first or second switch means are activated by voltage detecting means coupled to the output terminals upon detection of a failure of the second pair or first pair of voltage sources, respectively.

United States Patent 91 Tam 1111 3,748,500 [451 July 24,1973

1 1 MULTIPLE REDUNDANT POWER SUPPLY [76] Inventor: Ford Tam, 810Chestnut St.,

Birmingham, Mich. 48008 [22] Filed: Dec. 22, 1971 [21] Appl. N0.:210,720

Primary Examiner-John W. Huckert Assistant Examiner-L. N. AnagnosArtqrng l ouis l5. MarmMarvin S. Gittes et al.

571 ABSTRACT A multiple redundant power supply for supplying asubstantially constant voltage to output terminals is disclosed inaccordance with the teachings of the present invention. A first pair ofvoltage sources is coupled to one output terminal and a second pair ofvoltage sources is coupled to another output terminal and connected inseries with the first pair of voltage sources. Steering diodes areprovided such that a series connection obtains between either one of thevoltage sources [56] References Cited included in the first pair andeither one of the voltage UNITED STATES PATENTS sources included in thesecond pair. First switch means 3 459 957 8/1969 Kelley 307/71intewnnects the Rage mums included in the first 3:207:966 9,1965Parking); 307/71 X pair and is adapted when activated to provide aseries 3,221,239 11/1965 Langmet 1 307/63 X connection between the firstpair voltage sources. Sec- 3,384,758 5/1968 Kelley 307/77 ond switchmeans interconnects the voltage sources in- 3,387,l94 6/1968 Banks 320/7X cluded in the second pair and is adapted when acti- 3,411,014 11/1968PPP 307/61 X vated to provide a series connection between the sec- 3 711/1969 Bmcldey 307/69 X ond pair of voltage sources. The first orsecond switch $1 means are activated by voltage detecting means cou-362O220 11/1971 l 307/66 X pled to the-output terminals upon detectionof a failure 3666961 5,1972 2, 307/65 of the second pair or first pairof voltage sources, re-

, S ectivel FOREIGN PATENTS OR APPLICATIONS p y 197,239 7/1965 Sweden307/71 8 Claims 1 nnwin! 119,147 11/1944 Australia 320/18 I 9 il I08 112g //0 H Xi! /04 I22 %///9 m9 l 7 -//3 ::/24

MULTIPLE REDUNDANT POWER SUPPLY This invention relates to power suppliesand, more particularly, to a multiple redundant power supply capable ofsupplying a substantially constant voltage notwithstanding a failure ofone or more voltage sources included therein.

Various electrical devices that derive energy from a dc. power supplyrequire that the voltage supplied by the power supply maintain asubstantially constant value over prolonged periods of time. Thesediverse devices encompass electronic circuits and systems utilized inspace exploration as well as surgically implanted devices adapted toregulate organic functions. A typical example of the latter is thePacemaker which provides for electrical stimulation and regulation ofthe heart. It is, of course, obvious that proper operation of thePacemakerelectronics is dependent upon a substantially constant voltagesupplied thereto by the implanted power supply. Furthermore, to obviatethe necessity of frequent replacements by surgical procedures, it isessential that the voltage sources included in the Pacemaker powersupply admit of excellent longevity characteristics. Accordingly, it ispreferable to employ mercury cells as the voltage source for thePacemaker and various other electronic devices wherein high reliabilityand longevity of the power supply are fundamental factors.

Although power supplies including mercury cells exhibit characteristicsthat are generally well suited for electronic devices such as thosedescribed hereinabove wherein frequent replacement of a voltage sourceis either impossible or undesirable, the possibility of prematurefailure of a mercury cell must be considered. The prior art hassuggested a redundant power supply comprised of two mercury cells andincluding a voltage multiplier to provide the necessary voltage forenergizing the electronic device. Further proposals have contemplatedthe use of a redundant power supply employing mercury cells arranged inpermutative series combination. An attendant disadvantage of these priorart suggestions resides in the fact that although a substantiallyconstant voltage is provided in the event of a failure of a singlevoltage source, there is no protection against the deleterious effectsoccasioned by the failure of two voltage sources. Moreover, in powersupplies that are surgically implanted, such as those that find readyapplication with the Pacemaker, there has heretofore been nocontemplation of a simple and reliable technique to facilely examine theoperability of the voltage sources included therein.

Therefore, it is an object of the present invention to provide amultiple'redundant power supply for supplying a substantially constantvoltage notwithstanding a failure of one or more of the voltage sourcesincluded in the power supply.

It is another object of the present invention to provide a multipleredundant power supply including externally operable means for examiningthe operating characteristics of the voltage sources included in thepower supply.

A further object of this invention is to provide a power supplyadmitting of high reliability and longevity and adapted for surgicalimplantation in an organism.

Yet another object of the present invention is to provide a surgicallyimplantable power supply wherein investigation of the operativenessthereof does not require removal from an organism.

An additional object of this invention is to provide a multipleredundant power supply capable of supplying a substantially constantvoltage when all but any two of the voltage sources therein have failed.

A still further object of this invention is to provide a multipleredundant power supply including means for rearranging the circuitconnections of the voltage sources included therein upon detecting thefailure of two of such voltage sources.

Various other objects and advantages of the invention will become clearfrom the following detailed description of an exemplary embodimentthereof and the novel features will be particularly pointed out inconnection with the appended claims.

In accordance with this invention, a multiple redundant power supply isprovided wherein a substantially constant voltage is supplied to outputterminals notwithstanding a failure of one or more voltage sourcesincluded in said power supply, and comprising a first pair of parallelcoupled voltage sources coupled to one output terminal; a second pair ofparallel coupled voltage sources coupled to another output terminal andconnected in series with said first pair of parallel coupled voltagesources; said first and second pairs of voltage sources being providedwith steering diodes to permutatively establish series connectionsbetween any one voltage source in said first pair and any one voltagesource in said second pair; a first switch means interconnecting theparallel coupled voltage sources in cluded in said first pair andadpated when activated to provide a series connection between said firstpair of parallel coupled voltage sources; a second switch meansinterconnecting the parallel coupled voltage sources included in saidsecond pair and adapted when activated to provide a series conectionbetween said second pair of parallelcoupled voltage sources; and voltagedetecting means coupled to said output terminals for detecting a failureof the first pair of voltage sources or the second pair of voltagesources and responsive to said detected failure for activating saidsecond switch means or said first switch means, respectively.

The invention will be more clearly understood by ref erence to thefollowing detailed description of an exemplary embodiment thereof inconjunction with the accompanying drawing which schematicallyillustrates a multiple redundant power supply in accordance with thepresent invention.

Referring now to the drawing there is schematically illustrated a firstpair of voltage sources 10 comprised of a first volage source 101, asecond voltage source 102 and steering diodes and 106, a second pair ofvoltage sources 11 comprised of third voltage source 103, fourth voltagesource 104 and steering diodes 107 and 108. Each of voltage sources101-104 may comprise any suitable d.c. source such as a conventionalbattery, a mercury cell or the like. The steering diodes 105-108 maycomprise conventional semi-conductor unidirectional current conductingdevices such as germanium diodes, silicon diodes or suitably biasedtransistors. It may be observed that the combination of voltage source101 and diode 105 is parallel connected to the combination of voltagesource 102 and diode 106. Similarly, the combination of voltage source103 and diode 107 is parallel connected to the combination of voltagesource 104 and diode 108.

The first and second pairs of voltage sources and 11 are connected inseries relationship between output terminals A and B. More particularly,it may be readily observed that four distinct series paths extendbetween output terminals A and B. Thus, a first series path is comprisedof the series connection of output terminal A, steering diode 105, firstvoltage source 101, steering diode 107, third voltage source 103 andoutput terminal B. A second series path extends from output terminal Athrough steering diode 105, through first voltage source 101, throughfourth voltage source 104, through steering diode 108 to output terminalB. A third series path extends from output terminal A through secondvoltage source 102, through steering diode 106, through steering diode107, through third voltage source 103 to output terminal B. And a fourthseries connection is comprised of output terminal A, second voltagesource 102, steering diode 106, fourth voltage source 104, steeringdiode 108 and output terminal B. It should be noted that steering diodes105-108 preclude any circulating currents from flowing between theparallel coupled voltage sources included in each pair of voltagesources. Thus, if a voltage source 101 fails so as to provide a shortcircuit, steering diode 105 is poled such that current cannot flow fromvoltage source 102, through steering diode 106, through shortcircuitedvoltage source 101 and through steering diode 105. It is apparent thatthe remaining steering diodes 106-108 are poled in an analogous mannerto prevent the flow of current through a short-circuited voltage sourcein the event of failure.

If it is assumed that the voltage supplied by each voltage source101-104 is equal to E then the illustrated configuration of seriesconnected pairs 10 and 11 provides a substantially constant voltage 2Eacross output terminals A and B, even in the event of a failure of anysingle voltage source. Thus, if voltage source 101 fails, an outputvoltage equal to 2E will be provided from output terminal A, throughvoltage source 102 through steering diode 106, through steering diode107, through voltage source 103 to output terminal B. An alternativepath results in an output voltage equal to 2E from output terminal A,through voltage source 102, through steering diode 106, through voltagesource 104, through steering diode 108 to output terminal B. Similarly,should voltage source 102 fail, an output voltage 2E is provided fromoutput terminal A through steering diode 105 through voltage source 101and then, alternatively, through steering diode 107 and voltage source103 or through voltage source 104 and steering diode 108, to outputterminal B. Now, should voltage source 103 fail, an output voltage 2B isprovided from output terminal A, through steering diode 105 throughvoltage source 101, through voltage source 104, through steering diode108 to output terminal B. Alternatively, the output voltage 2B isderived from output terminal A through voltage source 102, throughsteering diode 106, through voltage source 104, through steering diode108 to output terminal B. Finally, if voltage source 104 fails, theoutput voltage 2E may be derived from the alternate paths consisting ofoutput terminal A, steering diode 105 and voltage source 101, or voltagesource 102 and steering diode 106, and then through steering diode 107and voltage source 103 to output terminal B.

It should now be appreciated that the series connection of pairs ofvoltage sources 10 and 11 as illustrated herein provide a substantiallyconstant voltage 2E in the event of a failure of one of the voltagesources 101-104. The illustrated configuration further provides asubstantially constant output voltage 2E in the event of a failure ofone voltage source in each pair of voltage sources. Thus, if voltagesources 101 and 103 fail to operate, an output voltage 2B is providedfrom output terminal A, through voltage source 102, through steeringdiode 106, through voltage source 104, through steering diode 108 tooutput terminal B. It is noted that steering diodes 105 and 107 aredisposed to prevent a short-circuiting of the output terminals A and Bif voltage sources 101 and 103 exhibit a short-circuiting failure.Similarly, if voltage sources 101 and 104 fail, the output voltage 2E isprovided from output termina A, through voltage source 102, throughsteering diode 106, through steering diode 107, through voltage source103 to output terminal B. Steering diodes 105 and 108 are here providedto prevent the shortcircuiting of output terminals A and B. Likewise, ifvoltage sources 102 and 103 should fail, the output voltage 2E isprovided from output terminal A, through steering diode 105 throughvoltage source 101, through voltage source 104, through steering diode108 to output terminal B. Short circuiting of the output terminals A andB is prevented by steering diodes 106 and 107. Finally, in the event offailure of voltage sources 102 and 104, the output voltage 2E is derivedfrom output terminal A, through steering diode 105, through voltagesource 101, through steering diode 107, through voltage source 103 tooutput terminal B; and short circuiting of the output terminals isprevented by steering diodes 105 and 107.

It is a feature of the present invention to provide the output voltage2E across terminals A and B in the event of a failure of the first pairof voltage source 10 or the second pair of voltage sources 11. Moreparticularly, should voltage sources 101 and 102 both fail, then meansare provided to connect voltage sources 103 and 104 in series aidingrelationship across output terminals A and B. Similarly, should bothvoltage sources 103 and 104 fail, then means are provided to connectvoltage sources 101 and 102 in series aiding relationship across outputterminals A and B. in accordance with the instant invention, switchmeans 109 interconnects the negative terminal of voltage source 101 andthe positive terminal of voltage source 102. Switch means 109 is hereillustrated as a saturable transistor means adapted when activated toprovide a series connection between voltage sources 101 and 102.Alternatively, switch means 109 may comprise other conventionalswitching devices such as a relay or the like. The control electrode ofswitch means 109, Le, the base electrode of the transistor means or theenergizing coil of the relay means, is coupled through diode 117 to avoltage detecting means further described hereinbelow. Similarly, switchmeans 110 interconnects the negative terminal of. voltage source 103 andthe positive terminal of voltage source 104. The switch means 110 issimilar to switch means 109 and is coupled via diode 118 to the soon tobe described voltage detecting means.

The aforementioned voltage detecting means is comprised of complementarytransistor means 113 and 114 coupled across output terminals A and B.Transistor means 113 is supplied with a bias potential whereby thetransistor means normally assumes a saturating condition in the absenceof a failure of the first pair or the second pair 11 of voltage sources.Accordingly, transistor means 113 includes a base electrode coupled toline 115 through current limiting resistance means 116. It is recognizedthat line 115 is coupled to the junction formed by the series connectionof the first and second pairs 10 and 11 of voltage sources and,therefore, is normally provided with a bias potential equal to onehalfthe output voltage 2E. Transistor means 113 includes an emitterelectrode connected to output terminal A and a collector electrodeconnected via series connected resistance means 121 and 122 to outputterminal B. The common connection of resistance means 121 and 122 isconnected to the base electrode of transistor means 114. The emitterelectrode of transistor means 114 is connected to output terminal B andthe collector electrode of transistor means 114 is connected to outputterminal A via resistance means 123. The collector electrode ofelectrode means 114 is additionally connected in common relationship tothe cathode of diode 117 and the anode of diode 118. A further diode 120is additionally provided between the base electrode of transistor means114 and line 115 for a purpose soon to be described. A d.c. isolatingcapacitor 124 is provided across output terminals A and B. In addition,series connected diodes 111 and 112 are connected across outputterminals A and B.

In operation, when neither the first pair of voltage sources 10 nor thesecond pair of voltage sources 11 has failed, output terminals A and Bare provided with an output voltage 2E and line 115 receives a voltageE. The base-emitter voltage drop across transistor means 113 istherefore sufficient to drive the transistor means into saturation.Accordingly, current flows from terminal B through series connectedresistance means 121 and 122 through transistor means 113 to outputterminal A. The series connected resistance means 121 and 122 form avoltage dividing circuit whereby the voltage applied to the baseelectrode of transistor means 114 is less than the voltage 2E applied tothe emitter electrode thereof. Resistance means 121 and 122 may beselected to provide any suitable base voltage to transistor means 114.Accordingly, transistor means 114 is similarly driven into saturationwhereby the voltage present at the collector electrode thereof is equalto the output voltage 2E applied to the emitter electrode thereof. Itshould be recognized that this effect may be obtained if resistancemeans 122 were provided in the emitter circuit of the saturatedtransistor means 113 and the base electrode of transistor means 114 wereconnected to the collector electrode of transistor means 113. Thevoltage 2E is applied by diode 118 from the collector electrode oftransistor means 114 to switch means 110. If, for purposes ofexplanation, it is assumed that switch means 110 comprises a transistormeans itis observed that the voltage applied to the Let it now beassumed that the first pair of voltage sources 10 fail. Thus, voltagesources 101 and 102 may each be openor short-circuited. The voltageprovided at line is thus reduced to zero and transistor means 113 isdriven out of saturation to assume its cutoff state. Accordingly,current ceases to flow through the collector circuit of transistor means113 and the voltage applied to the base electrode of transistor means114 is substantially equal to the voltage applied to the emitterelectrode thereof. Hence, transistor means 114 is driven out of itssaturation state and assumes its cutoff state. It is thereforeappreciated that the voltage applied from the collector electrode oftransistor means 114 to the base electrode of transistor means 110,which voltage is substantially equal to zero, is sufficiently less thanthe voltage applied to the emitter electrode of transistor means 110whereby a current circulating path is established from the positiveterminal of voltage source 104, through the emitter-base junction oftransistor means 110, through current limiting resistance means 119, toline 115, to the negative terminal of voltage source 104. Hence,transistor means 110 is driven into saturation and a short-circuitseries connection is established between the negative terminal ofvoltage source 103 and the positive terminal of voltage source 104.Consequently, an output voltage 2E is derived from output termianl A,through diode 111, through line 115, through voltage source 104, throughthe emitter-collector junction of saturated transistor means 110,through the voltage source 103 to output terminal B. Steering diodes 107and 108 are suitably poled to prevent currents from circulating from thepositive terminal of voltage source 104, through the emitter-collectorjunction of transistor means 110, to the negative terminal of voltagesource 104 and, similarly, to prevent currents from circulating from thepos itive terminal of voltage source 103, through the emit ter-collectorjunction of transistor means 110, to the negative terminal of voltagesource 103.

Let it now be assumed that the pair of voltage sources 1 1 fails. Thevoltage momentarily applied across terminals A and B, as well as thevoltage applied to line 115, is reduced to E. The base-emitter biaspotential of transistor means 113 is thus sufficient to maintain thetransistor means in saturation. Accordingly, the voltage divisioneffected by resistance means 121 and 122 would appear to provide avoltage less than E to the base electrode of transistor means 114whereas the emitter electrode of transistor means 114 maintains avoltage E. However, diode is poled so as to supply the voltage providedat line 115, which voltage is greater than the voltage division effectedby resistance means 121 and 122, to the base electrode of transistormeans 114. Consequently, the voltages applied to the base and emitterelectrodes of transistor means 114 are substantially equal so as todrive the transistor means into its cutoff state. Consequently, thevoltage appearing at the collector electrode of transistor means 114 issubstantially equal to zero. Transistor means 109 is thus suitablybiased to permit current to now flow from the positive terminal ofvoltage source 102, through the emitter-base junction of transistormeans 109, through diode 117, through resistance means 123 to the negative terminal of voltage source 102. Consequently, transistor means 109is driven into saturation and a series connection is established betweenthe negative terminal of voltage source 101 and the positive terminal ofvoltage source 102. An output voltage of 2E is now derived from outputterminal A, through voltage source 102, through saturated transistormeans 109, through voltage source 101, through line 115, through diode112 to output terminal B. It may be observed that steering diodes 105and 106 are suitably poled in a manner previously described with respectto steering diodes 107 and 108 such that circulating currents areprevented from flowing in the two loops now established in the firstpair of voltage sources 10.

It should now be readily appreciated that transistor means 113 includedin the voltage detecting circuit functions as a control transistor todetermine the state assumed by transistor means 114 in response to adetected failure of one pair of voltage sources. Further more, diode 120may comprise a suitable unidirectional current conducting device,including a biased transistor, to maintain the transistor means 114 inits cutoff state upon detecting a failure of the pair of voltage sources11. It is recognized by those of ordinary skill in the art that thismaintains transistor means 114 in its cutoff state when the pair ofvoltage sources 11 should fail. Furthermore, diodes 111 and 112 maycomprise conventional uni-directional current conducting devices such asaforedescribed steering diodes 105-108.

In view of the foregoing description of the invention schematicallyillustrated herein, it should now be readily apparent that the instantinvention admits of desirable characteristics wherein the multipleredundant power supply may be surgically implanted in an organism andemployed with such devices as the Pacemaker. A distinct feature of thepresent invention resides in the adaptability thereof to an examinationof the operativeness of the voltage sources 101-104 without thenecessity of surgically removing the power supply. Accordingly, amagnetically sensitive reed switch 125 is connected in parallelrelationship with the baseemitter junction of transistor means 113. Itis appreciated that switch 125 is operable in response to a magneticfield that may be generated in the vicinity thereof by a proximatelydisposed magnetic source such as a permanent magnet, an electro-magnetor the like. Thus, switch 125 may be closed by the appropriatepositioning by an operator of a suitable magnet. The closure of switch125 is effective to maintain the base electrode and the emitterelectrode of transistor means 113 at a common potential. Accordingly,transistor means 113 is driven from its saturation state to its cutoffstate. It is recalled that when transistor means 113 assumes its cutoffstate, transistor means 114 is driven out of saturation to likewiseassume its cutoff state. Thus, diode 117 applies an essentially zerovoltage to the base electrode of transistor means 109, whereas theemitter electrode thereof is maintained at a voltage equal to E.Similarly, the reduction in voltage applied to diode 118 by thecollector electrode of transistor means 114 is effective to enable thevoltage E appearing at line 115 to be applied to the base electrode oftransistor means 110 via current limiting resistance means 119, whereasthe voltage applied to the emitter electrode of transistor means 110 byvoltage source 104 is substantially equal to 2E. Consequently,transistor means 109 and 110 assume their respective saturation statesresulting in the series connections between voltage source 101 andvoltage source 102 and between voltage source 103 and voltage source104, respectively. It may therefore be observed that a currentconducting path exists between output terminal A, through voltage source102, through the emitter-collector junction of saturated transistormeans 109, through voltage source 10] through voltage source 104,through the emittercollector junction of saturated transistor means 110,through voltage source 103 to output terminal B. It is appreciated thatwhen transistor means 109 and 110 assume their respective saturationstates, the impedance exhibited thereby is sufficiently small such thatthe respective steering diodes 105108 are effectively by-passed, Hence,only minimal current flows through the steering diodes.

The operativeness of voltage sources 101-104 may now be examined merelyby detecting the voltage between output terminals A and B. If it isassumed that the voltage produced by each of the voltage sources isequal to E, then an output voltage 4E is indicative of the properoperating condition of each voltage source, an output voltage of SE isindicative of the failure of one voltage source and an output voltage of2E is indicative of the failure of two voltage sources. Hence, theoutput voltage applied to output terminals A and B is a directrepresentation of the operability of the voltage sources 101-104.Alternatively, the electronics of the Pacemaker" that may be utilizedwith the power supply of the instant invention may be particularlydesigned to exhibit voltage responsive characteristics that provide aready indication of the operating condition of the voltage sources101-104. Accordingly, the frequency of the signal produced by thePacemaker" may be proportional to the voltage applied to outputterminals A and B whereby a maximum frequency is produced when thevoltage produced by the series connected voltage sources 101-104 is amaximum and said frequency decreases as the voltage produced by theseries connected voltage sources decreases. Alternatively, the signalproduced by the Pacemaker may exhibit a pulse width that is linearlyproportional to the voltage produced by the series connected voltagesources 101-104. Furthermore, the signal produced by the Pacemaker" maybe a pulse having an amplitude that is proportional to the voltageproduced by the series connected voltage sources. It is understood thatthe operation of the Pacemaker" in response to the voltage applied tooutput terminals A and B may be readily ascertained by employingconventional EKG or other monitoring equipment.

If the power supply of the present invention admits of an applicationnot requiring the surgical implantation thereof in an organism, it isappreciated that the operativeness of voltage sources 101-104 may,nevertheless, be examined in a manner similar to that just described.However, switch may then comprise any conventional manually operableswitch means well known to those of ordinary skill in the prior art.

In the foregoing description, the voltage drops across each of thediodes herein have not been taken into account. It should be noted,however, that the effects attributed to such voltage drops arenegligible. Moreover, these negligible effects may be further minimizedby selecting suitable diodes exhibiting desirably low forward biasingcharacteristics. Alternatively, the voltages produced by each of thevoltage sources 101-104 may be relatively large in comparison to theforward voltage drop experienced by each diode, whereby the effects ofsuch forward voltage drop are seen to be insignificant.

While the invention has been particularly shown and described withreference to a specific embodiment thereof, it will be obvious to thoseskilled in the art that various changes and modifications in form anddetails may be made without departing from the spirit and scope of theinvention. It is therefore intended that the appended claims beinterpreted as including all such changes and modifications.

What is claimed is:

1. A multiple redundant power supply for supplying a substantiallyconstant voltage to output terminals notwithstanding a failure of one ormore voltage sources included therein comprising:

a first pair of voltage sources coupled to one output terminal;

first switch means interconnecting the voltage sources included in saidfirst pair and adapted when activated to provide a series connectionbetween said voltage sources included in said first pair;

a second pair of voltage sources coupled to another output terminal andconnected in series with said first pair of voltage sources whereby aseries connection is provided between either one of the voltage sourcesincluded in said first pair and either one of the voltage sourcesincluded in said second pair;

second switch means interconnecting the voltage sources included in saidsecond pair and adapted when activated to provide a series connectionbetween said voltage sources included in said second pair; and

voltage detecting means coupled to said output terminals for selectivelydetecting a failure of said first or second pairs of voltage sources andfor activating said second or first switch means, respectively, saidvoltage detecting means including first transistor means adapted toassume a first state when neither said first pair nor said second pairof voltage sources has failed and a second state when said first pair orsaid second pair of voltage sources has failed; and controltransistormeans coupled to said first transistor means for controlling the stateassumed by said first transistor means; said control transistor meansbeing coupled to the series connection of said first and second pairs ofvoltage sources for receiving a bias voltage therefrom.

2. The multiple redundant power supply of claim 1 further includingfirst and second uni-directional current conducting means connected inparallel relationship with said first and second pairs of voltagesources, respectively, for selectively providing a first conducting pathbetween said one output terminal and said second pair of voltage sourceswhen said first pair of voltage sources fails and a second conductingpath between said other output terminal and said first pair of voltagesources when said second pair of voltage sources fails.

3. The multiple redundant power supply of claim 2 wherein said first andsecond switch means each comprise transistor means having collector andemitter electrodes coupled to the respective voltage sources included inthe associated pair of voltage sources and a base electrode coupled tosaid first transistor means and responsive to the state assumed thereby.

4. The multiple redundant power supply of claim 3 further includingoperable switch means coupled to said control transistor means forde-energizing said control transistor means thereby forcing said firsttran-- sistor means to assume said second state whereby a se' riesconnection is provided between said voltage sources included in saidfirst pair and a series connection is provided between said voltagesources included in said second pair.

5. The multiple redundant power supply of claim 3 wherein said firsttransistor means and said control transistor means comprisecomplementary transistors each including a base electrode, said baseelectrode of said control transistor means being coupled to said seriesconnection of said first and second pairs of voltage sourcesand saidbase electrode of said first transistor means being coupled to thecollector electrode of said control transistor means.

6. A multiple redundant power supply for supplying a substantiallyconstant voltage to output terminals notwithstanding a failure or one ormore voltage sources included therein comprising:

first and second voltage sources coupled in parallel relationship to oneoutput terminal;

third and fourth voltage sources coupled in parallel relationship toanother output terminal and connected in series with said first andsecond parallel connected voltage sources whereby a series connection isprovided between either one of said first and second voltage sources andeither one of said third and fourth voltage sources;

voltage detecting means coupled to said output terminals for selectivelydetecting a failure of both said first and second voltage sources orboth said third and fourth voltage sources;

first switch means interconnecting said first and second voltage sourcesand adapted when activated by said voltage detecting means upon thedetection of a failure of both said third and fourth voltage sources toprovide a series connection between said first and second voltagesources; and

second switch means interconnecting said third and fourth voltagesources and adapted when activated by said voltage detecting means uponthe detection of a failure of both said first and second voltage sourcesto provide a series connection between said third and fourth voltagesources.

7. The multiple redundant power supply of claim 6 including furtherswitch means for simultaneously activating said first and second switchmeans to provide a series connection between said output terminals andsaid first, said second, said third and said fourth voltage sources,whereby the operativeness of said voltage sources may be examined.

8. The multiple redundant power supply of claim 7 wherein said furtherswitch means comprises magnetically sensitive switch means.

1. A multiple redundant power supply for supplying a substantially constant voltage to output terminals notwithstanding a failure of one or more voltage sources included therein comprising: a first pair of voltage sources coupled to one output terminal; first switch means interconnecting the voltage sources included in said first pair and adapted when activated to provide a series connection between said voltage sources included in said first pair; a second pair of voltage sources coupled to another output terminal and connected in series with said first pair of voltage sources whereby a series connection is provided between either one of the voltage sources included in said first pair and either one of the voltage sources included in said second pair; second switch means interconnecting the voltage sources included in said second pair and adapted when activated to provide a series connection between said voltage sources included in said second pair; and voltage detecting means coupled to said output terminals for selectively detecting a failure of said first or second pairs of voltage sources and for activating said second or first switcH means, respectively, said voltage detecting means including first transistor means adapted to assume a first state when neither said first pair nor said second pair of voltage sources has failed and a second state when said first pair or said second pair of voltage sources has failed; and control transistor means coupled to said first transistor means for controlling the state assumed by said first transistor means; said control transistor means being coupled to the series connection of said first and second pairs of voltage sources for receiving a bias voltage therefrom.
 2. The multiple redundant power supply of claim 1 further including first and second uni-directional current conducting means connected in parallel relationship with said first and second pairs of voltage sources, respectively, for selectively providing a first conducting path between said one output terminal and said second pair of voltage sources when said first pair of voltage sources fails and a second conducting path between said other output terminal and said first pair of voltage sources when said second pair of voltage sources fails.
 3. The multiple redundant power supply of claim 2 wherein said first and second switch means each comprise transistor means having collector and emitter electrodes coupled to the respective voltage sources included in the associated pair of voltage sources and a base electrode coupled to said first transistor means and responsive to the state assumed thereby.
 4. The multiple redundant power supply of claim 3 further including operable switch means coupled to said control transistor means for de-energizing said control transistor means thereby forcing said first transistor means to assume said second state whereby a series connection is provided between said voltage sources included in said first pair and a series connection is provided between said voltage sources included in said second pair.
 5. The multiple redundant power supply of claim 3 wherein said first transistor means and said control transistor means comprise complementary transistors each including a base electrode, said base electrode of said control transistor means being coupled to said series connection of said first and second pairs of voltage sources and said base electrode of said first transistor means being coupled to the collector electrode of said control transistor means.
 6. A multiple redundant power supply for supplying a substantially constant voltage to output terminals notwithstanding a failure or one or more voltage sources included therein comprising: first and second voltage sources coupled in parallel relationship to one output terminal; third and fourth voltage sources coupled in parallel relationship to another output terminal and connected in series with said first and second parallel connected voltage sources whereby a series connection is provided between either one of said first and second voltage sources and either one of said third and fourth voltage sources; voltage detecting means coupled to said output terminals for selectively detecting a failure of both said first and second voltage sources or both said third and fourth voltage sources; first switch means interconnecting said first and second voltage sources and adapted when activated by said voltage detecting means upon the detection of a failure of both said third and fourth voltage sources to provide a series connection between said first and second voltage sources; and second switch means interconnecting said third and fourth voltage sources and adapted when activated by said voltage detecting means upon the detection of a failure of both said first and second voltage sources to provide a series connection between said third and fourth voltage sources.
 7. The multiple redundant power supply of claim 6 including further switch means for simultaneously activating said first and second switch means to provide a series connection between said output terminals and said first, said Second, said third and said fourth voltage sources, whereby the operativeness of said voltage sources may be examined.
 8. The multiple redundant power supply of claim 7 wherein said further switch means comprises magnetically sensitive switch means. 